This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
This disclosure relates to apparatuses and methods for connecting sections of a subsea stack in offshore drilling environments. More specifically, the disclosure relates to pressure-energized ring joint gaskets such as a CX-type gasket that maintains its seal between stack sections during unbalanced drilling conditions such as when the external sea water pressure is greater or less than the internal well pressure.
CX gaskets are generally frustoconical in shape, with the cylindrical inner surface oriented toward the stack sections. The CX gasket also has wings that gradually taper away from the cylindrical inner surface and end in a rectangular shoulder. The outer surface of the CX gasket is metal, which helps to insure the integrity of the seal against the metal sections of the stack and that the sections can be disconnected when necessary for operational safety. The remainder of the gasket may be comprised of metal, plastic, or other materials that are known in the art.
FIG. 1 and FIG. 2 show, in cross-section, two sections 10 of a subsea stack joined by a clamp 20, the clamp 20 having two hubs 30, and a CX gasket 40. The internal well pressure is greater than the external sea water pressure. As a result, the wings 50 of the CX gasket 40 are forced against the hubs 30 of the clamp 20, which increases the metal-to-metal contact of the CX gasket 40. There is no deformation of the CX gasket 40 and the seal between the CX gasket 40 and the stack sections 10 remains intact.
In comparison, FIG. 3 and FIG. 4 show, in cross-section, two sections 10 of the stack joined by a clamp 20 when the internal well pressure is less than the external sea water pressure. In this case, the external sea water pressure causes the wings 50 of the CX gasket 40 to deflect inwardly away from the hubs 30 of the clamp 20. This decreases the metal-to-metal contact of the CX gasket, breaks the seal between the metal sections 10 of the stack, and creates a leak path which, depending on the relative internal well pressure and external sea water pressure, may allow sea water to leak into the well bore or well bore fluids to leak into the surrounding environment.
There is a need for a CX gasket 40 for a clamp 20 or other connector that does not change shape and maintains its seal whether the internal well pressure is greater or less than the external sea water pressure.